A cellular wireless network may include a number of base stations that radiate to define wireless coverage areas, such as cells and cell sectors, in which user equipment devices (UEs) such as cell phones, tablet computers, tracking devices, embedded wireless modules, and other wirelessly equipped communication devices (whether or not technically operated by a human user), can operate. In turn, each base station may be coupled with network infrastructure, including one or more gateways and switches, that provides connectivity with one or more transport networks, such as the public switched telephone network (PSTN) and/or a packet-switched network such as the Internet for instance. With this arrangement, a UE within coverage of the network may engage in air interface communication with a base station and may thereby communicate via the base station with various remote network entities or with other UEs.
When a cellular wireless network serves UEs, the network may allocate various resources to facilitate communication to and from the UEs. In an example arrangement, for instance, the network may allocate “bearers” that define physical or logical communication channels extending between the UEs and a transport network. Each such bearer may include a radio-bearer component that extends between a UE and a serving base station and an access-bearer component that extends between the serving base station and the transport network. Further, each such bearer may have an associated service level, such as “best effort” or “guaranteed bit rate” for instance, to support a particular quality of service or type of service. In practice, the network may then allocate a number of such bearers for a UE, to support various different types of communication services.
By way of example, when the UE first enters into coverage of a base station, the UE may engage in a registration or “attachment” process that causes the network to allocate for the UE certain default bearers in accordance with the UE's service profile. For instance, if the UE's service profile indicates that the UE supports general packet-data communication (such as web browsing, file transfer, and the like), the network may allocate for the UE a default bearer for carrying such communications with a best-effort service level. Further, if the UE's service profile indicates that the UE supports voice over Internet Protocol (VoIP) communications or other such real-time packet-based communication service, the network may allocate for the UE a default bearer to support Session Initiation Protocol (SIP) signaling or the like to facilitate setup of such communications.
In turn, as a UE is being served by a base station, if the UE is going to engage in another type of communication service, the network may allocate for the UE still other bearers, possibly with other service levels. For instance, if the UE supports VoIP service and seeks to engage in a VoIP call, or a VoIP call server seeks to connect a call to the UE, the network may allocate for the UE a dedicated bearer having a guaranteed bit rate and perhaps other high service level attributes, to carry the VoIP bearer traffic (e.g., packets representing voice), and the UE may then engage in the VoIP call via that bearer. Further, if the UE supports online gaming service and seeks to engage in gaming communication, the network may allocate for the UE a dedicated bearer having a particular service level appropriate for that gaming communication, and the UE may then engage in the gaming via that bearer.
Each bearer that the network allocates to a UE may have an associated quality of service class indicator (QCI) or other indication of the bearer's service level. For instance, a bearer for carrying VoIP bearer traffic may have a QCI of 1, a bearer for carrying SIP signaling or the like may have a QCI of 5, and bearer for carrying best-effort traffic may have a QCI of 8 or 9. When a base station serves a UE, the base station may maintain a context record for the UE, identifying each bearer that the UE has, and specifying the QCI level and/or other attributes of the bearer, for reference by the base station to help ensure appropriate service of the UE.
In a typical cellular wireless network, each of a base station's coverage areas will operate on one or more carrier frequencies and will define various channels for carrying control and bearer data between the base station and the UEs served by the base station. The base station may then manage communication of packet data to and from served UEs over the air interface. For instance, as the base station receives packet data from the network infrastructure for transmission to UEs on various bearers, the base station may queue the data, schedule use of particular downlink air interface resources (e.g., channels, resource blocks, or the like) to carry the data, and transmit the data on the scheduled resources to the destination UEs. Likewise, as UEs have data to transmit on various bearers, the base station may schedule use of particular uplink air interface resources to carry the data, and the UEs may transmit the data on the scheduled uplink resources to the base station.
Optimally, a wireless service provider will strategically implement base stations throughout a market area so that served UEs can move between the base station coverage areas without loss of coverage. Each base station may include an antenna structure and associated equipment, and the wireless service provider may connect the base station by a landline cable (e.g., a T1 line) with the service provider's network infrastructure to enable the base station to communicate with a signaling controller (e.g., MME), gateway system, other base stations, and the like.
In practice, however, it may be impractical for a wireless service provider to run landline connections to base stations in certain locations. For instance, where a service provider seeks to provide many small coverage areas blanketing a market area or to fill in coverage holes between coverage of other base stations, the service provider may implement many small-cell base stations throughout the market area, but it may be inefficient or undesirable to run landline cables to every one of those small-cell base stations.
To connect a base station with the network infrastructure in such a situation, the wireless service provider may implement a wireless backhaul connection between the base station and another base station of the service provider's network. In this situation, the base station at issue operates as a relay base station, and the other base station operates as a donor base station. In practice, the relay base station includes or is coupled (e.g., via a local area network or other connection) with a UE, referred to as a relay-UE, and the donor base station then serves the relay-UE in much the same way that the donor base station serves other UEs. Further, the relay base station itself serves UEs, in much the same way that any base station would. For example, when a UE enters into coverage of the relay base station, the UE may signal to the relay base station to initiate an attach process, the UE may acquire an IP address, and an MME may engage in signaling to establish one or more bearers between the UE and a gateway system. Each of these bearers though, would pass via the wireless backhaul connection.